Department of Marine and Environmental Sciences, Marine Science Center, Northeastern University, 30 Nahant Road, Nahant, MA 01908, United States.
FEMS Microbiol Lett. 2023 Jan 17;370. doi: 10.1093/femsle/fnad082.
Long-term anthropogenic nitrate (NO3-) enrichment is a serious threat to many coastal systems. Nitrate reduction coupled with the oxidation of reduced forms of sulfur is conducted by chemolithoautotrophic microbial populations in a process that decreases nitrogen (N) pollution. However, little is known about the diversity and distribution of microbes capable of carbon fixation within salt marsh sediment and how they respond to long-term NO3- loading. We used genome-resolved metagenomics to characterize the distribution, phylogenetic relationships, and adaptations important to microbial communities within NO3--enriched sediment. We found NO3- reducing sulfur oxidizers became dominant members of the microbial community throughout the top 25 cm of the sediment following long-term NO3- enrichment. We also found that most of the chemolithoautotrophic genomes recovered contained striking metabolic versatility, including the potential for complete denitrification and evidence of mixotrophy. Phylogenetic reconstruction indicated that similar carbon fixation strategies and metabolic versatility can be found in several phylogenetic groups, but the genomes recovered here represent novel organisms. Our results suggest that the role of chemolithoautotrophy within NO3--enriched salt marsh sediments may be quantitatively more important for retaining carbon and filtering NO3- than previously indicated and further inquiry is needed to explicitly measure their contribution to carbon turnover and removal of N pollution.
长期人为硝酸盐 (NO3-) 富集会对许多沿海系统造成严重威胁。硝酸盐还原与还原态硫的氧化是由化能自养微生物种群进行的，这一过程减少了氮 (N) 污染。然而，对于能够在盐沼沉积物中进行固碳的微生物的多样性和分布，以及它们对长期硝酸盐负荷的响应方式，人们知之甚少。我们使用基因组解析宏基因组学来描述富硝酸盐沉积物中微生物群落的分布、系统发育关系和重要适应特征。我们发现，在长期硝酸盐富集后，硝酸盐还原硫氧化菌成为沉积物顶部 25 厘米范围内微生物群落的主要成员。我们还发现，大多数回收的化能自养基因组具有惊人的代谢多功能性，包括完全反硝化的潜力和混合营养的证据。系统发育重建表明，类似的固碳策略和代谢多功能性可以在几个系统发育群中找到，但这里回收的基因组代表了新的生物体。我们的研究结果表明，在富硝酸盐的盐沼沉积物中，化能自养作用的作用对于保留碳和过滤硝酸盐可能比以前所表明的更为重要，需要进一步研究来明确测量它们对碳周转和氮污染去除的贡献。
